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Transcript
```Generator and
Transformer
Moving Conductor
If a straight conductor is moved in a
path perpendicular to a magnetic field, a
current is induced in the conductor
Induced emf
=Blv
l – length of conductor
v – velocity of conductor
Example
An airplane travels at 1000 km/hr in
region where the Earth’s magnetic field
in
5.0 x 10-5 T. What is the emf
induced between the wing tips that are
70m apart?
Generators (Dynamo)
Transforms mechanical energy into electric
energy
Coil of wire spins in the presence of a
permanent magnetic field
Induces are current in the coil
Current produced actually fluctuates as the
coils position in the field changes
Max current when perpendicular to B
Min current when coil parallel to B (no
current)
Moving Electricity
How does electric energy transmit over
large distances?
How much power is wasted when
10000W of power is transmitted along a
cable with a resistance of 1 at 200V?
What would be lost if transmitted at
Much less lost when travels at a higher
V and lower I
Transformer
Device that changes voltages
Two coils around an iron core
Current supplied to the primary coil
induces a current in the secondary coil
By varying the number of windings in
the coils you can vary the potentials
Types
Step-up – more windings on the
secondary coil increases the voltage
Step-down – less windings on the
secondary coil decreases the voltage
Transformers work only on AC current.
Why?
Transportation
Electric energy is stepped up for
transmission and then stepped down for
household use
Most transformers are close to ideal
(100% efficient)
- low resistance
- very permeable rounded core
```
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